Process of improving carbon black



Aug. 13, 1935. E. H. DAMON PROCESS OF IMPROVING CARBON BLACK OriginalFiled June l5. l95l EN l@ Ressued Aug. 13, 1935 UNITED STATES PATENTOFFICE PROCESS F IMPROVING CARBON BLACK Original No. 2,005,022, datedJune 18. 1935. Serial No. 544.647, June 15. 1931.

Application for reissue June 20, 1935, Serial No. 27,555

Claims.

This invention relates to improvements in methods of treating carbonblack whereby certain selected characteristics may be imparted to it inaccordance with the use for which it is intended. In a broad aspect, myinvention consists in modifying the properties of commercial carbonblack by subjecting it to a controlled oxidation in such a manner as toincrease its oxygen content.

It has been appreciated for some time that various properties of carbonblack, such as color, length, ow, iridescence, tinting strength, etc.,may be varied or intensified by oxidation and this has been doneheretofore to a more or less imperfect extent in the impingement processof manufacturing carbon black by varying the interval which the carbonblack is allowed to remain upon the channel irons or rolls. Suchprocedure has, however, not only reduced the amount of yield but hasaffected some qualities of the carbon black adversely while improvingothers.

I have discovered that more eiiicient and accurate results may beachieved by subjecting carbon black, which has been produced underconditions resulting in maximum yield, to a supplementary and separateoxidizing treatment under controlled conditions. In carrying out myinvention I have secured satisfactory results by subjecting commercialcarbon black to heat within deiinite limits and agitation in thepresence of atmospheric oxygen.

The treatment contemplated by my invention is to be clearlydistinguished (l) from cracking, which consists in heating in anon-oxidizing atmosphere and may be represented by the reactio'n,CH4=CI2H2, (2l carbonization, which consist-s in heating with or withoutoxygen to cause selective distillation and oxidation of previouslyentrapped tarry bodies, and (3l combustion oi' carbon, which may berepresented by the reaction C-|-O2=CO2. On the contrary, the process ofmy invention is concerned primarily with the additionof oxygen or carbonoxides to carbon black, forming a stable union and thus producing a newproduct having altered properties and characteristics, I have to contendwith the combustion effects for commercial reasons only and havediscovered that, under favorable conditions, the reaction XC|Y0=CxOy canbe caused to proceed as fast as the combustion reaction, C+Oz=CO2.

The nature of my invention will be best understood and appreciated fromthe following description of one suitable form of apparatus for carryingthe process into effect. Such an apparatus is illustrated in theaccompanying drawing, ln which Fig. l is a perspective view in sideelevation with certain portions broken away, and

Fig. 2 is a view inperspective of the drum.

Referring to the drawing, it will be seen that the apparatus is enclosedwithin iire brick walls IB which constitute a combustion or burnerchamber. Supported in opposite walls of the chamber in suitable bearingsis a horizontally disposed drum I2 having at one end a reduced extensionI4 opening through one end Wall of the chamber and at the other beingsecured to a shaft IB car2 rying a sprocket wheel IB by which rotationmay be imparted to the shaft and the drum from any suitable source ofpower. The shaft I6 is journalled in a bearing member 2|) suitablymounted in one end Wall of the chamber and the extension I4 is arrangedto revolve in a bearing ring 22 built into the opposite end wall of thechamber. The body of the drum I2 is supported upon antifriction rolls 26carried by brackets 24 arranged symmetrically within the combustionchamber.

The large or right-hand end oi' the drum I2 contains a spider 28 havingopen sectors therein for the passage of air or gas and a hub for thereception of the shaft I6. Within the drum are secured two series ofvanes or fins 30, all of which are downwardly inclined toward the centerof the drum and which serve, as the drum is rotated, to pick up carbonblack from the mass contained therein and spill it back again, thusagtating it and continuously shifting it inwardly from both ends of thedrum toward the center there of. The result is that the carbon black isthoroughly exposed to and intimately mixed with the current of air orgas passing longitudinally through the drum.

An elongated gas burner 32 extends into the combustion chamber beneaththe drum I2 and this serves not only to heat the drum and the carbonblack contained therein but to create a current of hot gases which passinto the drum through the inlet openings of the spider 28 and outthrough the extension Il. An air intake opening 3l is provided beneaththe burner 32 and a stack 36 having a damper 38 projects from the roofof the combustion chamber whereby the gases may escape when the drum isbeing charged or emptied. The volume of gas flowing through the drum I2may be increased by partially opening the damper 38.

In carrying out the process of my invention, a charge of commercialcarbon black is introduced, into the drum through the inlet at the leitend thereof and the drum is then rotated continuously, maintaining theblack in a condition of constant agitation. If it is desired to improveand modify the properties of the carbon black for the purpose ofadapting it for use in the manufacture of printing inks, the burner maybe adjusted to maintain the drum at a temperature of 750 to 800 F.

The process is continued under these conditions for a period of 75minutes with a charge of about 50 pounds. Hot gases with considerableatmospheric oxygen pass through the drum l2 and are intimately mixedwith the hot carbon black as it is spilled about within the drum. Thetreatment improves the length of flow of the carbon black, removes itsoriginal iridescence, and best adapts its characteristics of body andfluidity of mixture for use as an ingredient in ink. The carbon black isalso probably improved by the removal of traces of oils and hydrocarbonstherefrom. The reaction upon the carbon black is principally oxidation.The "va1ue or volatile matter in the resulting product is increased from5% to 13% as compared to the volatile content of the original material.The United States Bureau of Mines is authority for the statement thatthe volatile content of commercial carbon black runs from 5.33% to14.44%, although in practice a wider range is sometimes encountered. Inpracticing the present invention, in specific cases the volatile contentof commercial carbon black has been increased to from 5.7% to 16.32%,removing traces of oil and hydrocarbons in the process.

If it is desired to secure a product having a deeper color. the processmay be continued for a longer interval, for example, 90 minutes, andunder these circumstances the length and flow of the carbon black willbe somewhat reduced while the color will be modified as explained. Thecolor may be increased to a greater degree by prolonging the treatmentstill further. In other words, as the treatment is continued the lengthand flow of the carbon black reach a maximum and then begin to decrease,while color continues to improve. The treatment is accompanied bydefinite loss of weight in the charge of carbon black and this factormust be reckoned with in determining the practical commercial limits inthe time of treatment. A loss of approximately 35% due to combustion isto be expected under the conditions set forth above.

I have explained how the process of my invention may be carried out inmodifying certain characteristics of carbon black. I contemplate thatall the various characteristics or properties of carbon black may beadvantageously modified and among these properties I include color,length. flow, iridescence, top tone, under tone, tinting strength, valueor amount of volatile matter, capacity for absorption or adsorption, andactivity. These properties may be affected by suitably varying thedifferent factors of the process, such as temperature, character offlame, and composition of flue gases, stirring of material, speed ofdrum rotation, and time. These factors are more or less interdependentbut may be varied to give the results best suited for requirements ofeach particular case. For example, temperatures between 600 and 1000 F.have been employed with satisfactory results in accordance with thecharacteristics desired in different products. 'I"he addition of oxygento carbon black is slowly effected at the lower temperatures but takesplace rapidly at the higher temperatures. 'I'he lower temperaturesemployed are, therefore, limited by the practical considerations ofcommercial output while, to a large extent, the higher temperatures arelimited by the diiIiculties incident to accurate control of theoxidation process. In all cases, however, the method of my invention iscarried out at temperatures below those at which calcining of the carbonblack can occur, i. e., below 1200 F., and at such temperatures there isno loss of the volatile content of the carbon black.

It will be understood that the apparatus illustrated is typical only ofone satisfactory construction and that in practice it may be modified inarrangement and operation from that described. For example, the burnermay be arranged to heat the drum indirectly, as in a muilie furnace, andthe air ports may be located in different parts of the combustionchamber from those shown.

The term carbon black is used herein as including within its scope anyblack suitable for the raw material of ink or which has the propertiesoi the carbon black of commerce.

Having thus described my invention, what I claim as new and desire tosecure by Letters Patent is:

1. The method of treating carbon black to modify its properties, whichconsists in subjecting a measured volume thereof to the action of heatnot exceeding 1000 degrees F. and oxygen in controllable quantities, andsimultaneously causing an agitation of the carbon black for an intervalduring which the stable oxygen content of the carbon black is increased.

2. The method of treating carbon black to modify its properties, whichconsists in confining a measured volume thereof within ahorizontallydisposed drum, causing a surface iiow of the carbon black byrotating the drum, stirring the carbon black to expose fresh surfaces,and owing gases, including oxygen, of controllable composition over andthrough the carbon black, While maintaining the same at a temperature toincrease the oxygen content of the carbon black, all for a portion ofthe interval of time during which increase in oxygen content occurs.

3. The method of increasing the length and flow of carbon black for usein printing inks. kwhich consists in subjecting it to the controlledaction of an oxidizing gas while maintained at a temperature of 'Z50-800degrees F. for a period of approximately 75 minutes, thereby increasingthe oxygen content of the carbon black which is not eliminated bycombustion in the treatment.

4. The method of increasing the volatile content of carbon black, whichconsists in agitating a measured charge thereof and slowly oxidizing thesame at a temperature not exceeding 1000 degrees F., incidentallyeliminating some carbon black by combustion.

5. The method of intensifying the color of carbon black, which consistsin continuously agitating a measured charge thereof and subjecting thesame to a slow oxidation at a temperature below that at which calciningtakes place but sufficiently high to increase the stable oxygen contentof the carbon black.

6. The method of treating carbon black to modify its properties, whichconsists in subjecting commercial carbon black to the action of heat notexceeding 1000 degrees F. and oxygen in controllable quantities, andsimultaneously causing an agitation of the carbon black for an intervalduring which the stable oxygen content of the carbon black is increased.

7. The method of treating carbon black to modlfy its properties, whichconsists in confining cominercia] carbon black within ahorizontally-disposed drum, causing a surface flow oi' the carbon blackby rotating the drum, stirring the carbon black to exposefresh surfaces,and iiowing gases, including oxygen, of controllable composition overand through the carbon black, while maintaining the same at atemperature to increase the oxygen content of the carbon black, all fora portion oi' the interval of time during which increase in oxygencontent occurs.

8. The method of increasing the volatile content of carbon black, whichconsists in agitating commercial carbon black and slowly oxidizing thesame at a. temperature not exceeding 1000 degrees F., incidentallyeliminating some carbon black by combustion.

9. The method of intensifying the color of carbon black, which consistsin continuously agitating commercial carbon black and subjecting thesame to a slow oxidation at a temperature below that at which calciningtakes place but sumciently high to increase the stable oxygen content ofthe carbon black.

10. The method of treating carbon black to modify its properties, whichconsists in continuously agitating commercial carbon black andsubjccting the same to a slow oxidation at a temperature below that atwhich calcining takes place but suiliciently high to increase the stableoxy- 15 gen cont/ent of the carbon black,

EDWARD H. DAMON.

